For future scaling of flash (non-volatile) memory devices, the inter-poly dielectric or blocking dielectric layers should be made of a dielectric material with a higher κ-value than Al2O3 and, at the same time, a band gap comparable or preferably larger than Al2O3. A class of materials that may be able to fulfill these requirements is the class of rare-earth (lanthanide) aluminates, i.e. alloys of rare-earth oxides with Al2O3.
US2008/0185633A1 discloses a charge trap memory device comprising: a tunnel insulating layer on a substrate; a charge trap layer on the tunnel insulating layer; and a blocking insulating layer on the charge trap layer, wherein the blocking insulating layer may be formed of a material including a lanthanide (Ln) so as to have a higher dielectric constant and a larger energy band-gap. Ln may refer to the 15 elements ranging from lanthanum (La) as the 57th element to lutetium (Lu) as the 71st element. The blocking insulating layer may further include aluminum and oxygen, wherein the ratio of lanthanide to aluminum may be greater than 1 (e.g., about 1.5 to about 2).
In particular, the application discloses LaAlO having an energy band-gap and a dielectric permittivity (κ) depending on the La/Al composition. LaAlO3 with a La/Al composition ratio of 1 may have an energy band-gap of about 5.65 eV and a dielectric permittivity (κ) of about 12, while La4Al2O9 with a La/Al composition ratio of 2 may have an energy band-gap of about 5.95 eV and a dielectric constant of about 20.
Although the performance of the lanthanum aluminates (LaAlO) disclosed in US2008/0185633A1 is superior to alumina in terms of dielectric permittivity (κ-value of thin film γ-Al2O3 is about 9), the band gap achieved is lower than that of thin film γ-Al2O3 (about 6.0-6.5 eV) and still too low for the most advanced flash memory devices.
There is therefore still a need for a dielectric material and layer, and for a process of manufacturing thereof, wherein the dielectric material possesses a κ-value higher than Al2O3 whilst providing a band gap comparable or preferably larger than Al2O3.
Advantageously, the dielectric material and layer according to the disclosure allow manufacturing semiconductor devices, in particular flash memory devices, with improved performance and characteristics.
Other advantages and benefits provided by the dielectric material and layer according to the disclosure, will be apparent from the following description and the accompanying drawings.